Abstract:Underwater acoustic communication is a key technology in the field of underwater activities including underwater surveillance, underwater operations, and military actions. The complexity of the underwater communication channel strongly restricts underwater communication speed, distance, and reliability. Incoherent communication is more robust to channel variation and is wildly used today. Coherent communication is ten times faster than incoherent communication. But it is more vulnerable to channel variation. It is still under developing. To further improve underwater communication performance, the community is keeping improving adaptive equalization algorithms, error correction coding, etc., and developing new technologies like time reversal technology, MIMO technology, etc. Many Chinese organizations joined in the development of underwater communication and networking technology. They carried out theoretical researching, prototypes building, lake and sea trials, and achieved much progress. Especially in last fifteen years, with enhanced support from Chinese government funding, China shortened the gap in underwater communication and networking technology between the leading counties in the world but still at least five years behind them in both theory research and commercial product development. China needs to keep working hard in all fields of underwater communication including algorithm research, networking protocol design, more lake and sea trials, more application, hardware developing and commercial products developing.